A wire grid polarizer (WGP) can transmit one polarization (e.g. p-polarization) and reflect or absorb an opposite polarization (e.g. s-polarization).
High reflectivity (e.g. high Rs) of the opposite polarization can be important because some applications use both polarized light beams (e.g. s & p). High absorption/low reflectivity (e.g. low Rs) of the opposite polarization can be important in some applications because reflection of this polarization (Rs) can interfere with the optical system. For example, the reflected s-polarization can cause ghosting in an image projector. Some WGPs are designed for high reflection and others for high absorption of the s-polarization.
High transmission (e.g. high Tp) of one polarization can be an important feature of WGPs in order to minimize light-source power requirements. Low transmission (e.g. Ts) of the opposite polarization can be important for improved light image resolution. The quality or performance of WGPs can be shown by efficiency (Tp*Rs) and contrast (Tp/Ts).
WGP wires, especially for polarization of visible or ultraviolet light, can be small and delicate with nanometer-sized pitch, wire-width, and wire-height. WGPs are used in systems (e.g. computer projectors, semiconductor inspection tools, etc.) that require high performance. Small defects in the WGP, such as collapsed wires can significantly degrade system performance (e.g. distorted image from a computer projector). Therefore, it can be important to protect the wires from damage.